/Engine/Source/Editor/UnrealEd/Public/Features/IPluginsEditorFeature.h
Called to performadditionalpath validation when the path is modified (the bCanBePlacedInEngine validation will have already occurred and passed by this point)
virtual bool ValidatePathForPlugin ( const [FString](API\Runtime\Core\Containers\FString) & ProposedAbsolutePluginPath, [FText](API\Runtime\Core\Internationalization\FText) & OutErrorMessage )